The invention relates to a method of operating a metallurgical plant comprising a metallurgical vessel, such as a melting furnace or a converter, through the ceiling of which one or several hollow electrode(s) having a cavity are guided, in which cavity a supply pipe is liftably and lowerably moveable.
In order to obtain molten iron by the reduction of iron oxide ore, it was proposed in U.S. Pat. No. 3,163,521 to use a closed vessel provided with a refractory lining and including one or more Soderberg or graphite electrodes projecting through the ceiling of the vessel so as to produce an electric arc, a number of introduction shafts for the reduced material connected to the charging openings of the vessel in a gas-tight manner, and a number of refractorily lined reduction towers corresponding to the number of introduction shafts. From this U.S. patent, it is also known to provide one or more bored-through electrodes and to insert through the bore a liftable and lowerable supply means formed by concentric pipes to convey fuel, oxygen-containing gas and steam. According to the U.S. patent, a gas is produced with properties that do not have an oxidizing effect on iron, which gas is directly supplied to the reduction towers.
When melting low-alloyed and unalloyed scrap in an electric arc furnace, oxygen is an frequently introduced as additional source of energy. This supply of oxygen is able to assist substantially the melt-down process soon after the start of melting, if the O.sub.2 jet is directed to the surroundings of the electrodes. In particular, the carbon from the fluxes and silicon, as well as the carbon from the scrap, will burn. It is only when a metal sump has formed and the scrap has been sufficiently heated in the region affected by the oxygen jet that the burning of scrap can efficiently be started.
However, there are cases in which the melt-down process is assisted through the main door or the auxiliary door of the furnace via manually operated self-consuming oxygen lances with low consumption, or by using at least three oil - oxygen burners fixedly installed in the furnace wall between the so-called hot spots or guided through openings in the furnace lid. By these measures, charging times as short as possible are to be achieved, wherein the high transformer outputs, in particular of so called UHP-furnaces (ultra-high power furnaces with connected loads of up to 160 MVA), are to be utilized during almost the total turn-on time.
Manual operation of the oxygen lances results in a strong thermal load, thus increasing the risk of accidents for the operating personnel. The position of the reaction zone is not precisely defined, which may lead to an irregular attack of the refractory furnace lining. Furthermore, according to conventional technologies, the chance of damage to the electrodes cannot be excluded and, finally, the number of lances or burners that may be introduced is very limited.
The invention has as its object to eliminate the described disadvantages and difficulties in metal melting, and to allow the melting and the metallurgical treatment of various steel grades from scrap as well as of directly reduced sponge iron in a single metallurgical vessel in an operationally safe manner and with as low a consumption of energy and time as possible.